Intraluminal stents implanted with percutaneous methods have become a standard adjunct to procedures such as balloon angioplasty in the treatment of atherosclerotic disease of the arterial system. Stents, by preventing acute vessel recoil, improve long term patient outcome and have other benefits such as securing vessel dissections.
Intraluminal stents comprise generally tubular-shaped devices which are constructed to hold open a segment of a blood vessel or other anatomical lumen. Intraluminal stents are used in treatment of diseases such as atherosclerotic stenosis as well as diseases of the stomach and esophagus, and for urinary tract applications. Adequate stent function requires a precise placement of the stent over a lesion or site of plaque or other lumen site in need of treatment. Typically, the stent is delivered to a treatment site by a delivery catheter that comprises an expandable portion for expanding the stent within the lumen.
The delivery catheter onto which the stent is mounted may be a balloon delivery catheter similar to those used for balloon angioplasty procedures. In order for the stent to remain in place on the balloon during delivery to the site of damage within a lumen, the stent may be compressed onto the balloon. The catheter and stent assembly is introduced within a patient's vasculature using a guide wire. The guide wire is disposed across the damaged arterial section and then the catheter-stent assembly is advanced over the guide wire within the artery until the stent is directly within the lesion or the damaged section.
The balloon of the catheter is expanded, expanding the stent against the artery wall. The artery is preferably slightly expanded by the expansion of the stent to seat or otherwise fix the stent to prevent movement. In some circumstances during treatment of stenotic portions of the artery, the artery may have to be expanded considerably in order to facilitate passage of blood or other fluid therethrough. In the case of a self expanding stent, the stent is expanded by retraction of a sheath or actuation of a release mechanism. Self expanding stents may expand to the vessel wall automatically without the aid of a dilation balloon, although such a dilation balloon may be used for another purpose.
These manipulations are performed within the body of a patient by a practitioner who may rely upon both placement markers on the stent catheter and on the radiopacity of the stent itself. The stent radiopacity arises from a combination of stent material and stent pattern, including stent strut or wall thickness. After deployment within the vessel, the stent radiopacity should allow adequate visibility of both the stent and the underlying vessel and/or lesion morphology under fluoroscopic visualization.